[warbie]

My Beamax samples arrived the other day - 1.2 and 1.5 gain material. One of these was to replace my home made screen which has had everything from BW to all types of Screen Goo on it. Currently it just has a few coats of primer which, for my room/pj, is giving the best results so far. What has really surprised me is that the primer is not only considerably brighter than the 1.2 gain material, but also noticeably brighter than the 1.5. If these readings are accurate (which i'm starting to doubt) the primer easily has a gain of 1.8. The primer isn't as bright as the lumitec paint qute a few ppl have been experimenting with, but doesn't have the nasty white crush/blur (or whatever the technical term is).

I'll try and get some pictures up - lost the usb lead for my phone - but am now a little thrown. Are the Beamax readings way, way off? Is this some crazy bright primer? (Polycell bascoat complete for anyone who's interested). I was actually after something brighter after realising it wasn't lack of contrast making it hard to resolve dark scenes, but lack of lumens.

I'm not sure where i'm going with this ramble now, so will stop Any ideas guys?

[KelvinS1965]

I've got the 1.5 gain version, but I'm not really convinced it is 1.5, either that or my old 1.8 Greywolf screen was more than 1.8. I'm finding that the picture isn't as bright as I'd like (or as bright as it was before), but I'm using the dimer (but more accurate mode). Looks like I'll have to calibrate one of the brighter modes and hope it does the trick, or change my PJ for something brighter and with equal/better contrast.

My old screen was only slightly smaller (120" diagonal vs 128" diagonal 16:9 equivalent) and I even used to put an ND2 filter in front of the PJ to dim it down.

[custard10]

there have been a few cases of misreported gain

what i would say is the material you have from beamax is most likely angular/specular reflective so to see it performing to its true potential you would have to place yourself at the opposite angle to the incident light from the projector.

the lumitec (and most probably the polycell basecoat) is matt so it has diffuse reflective properties. this sort of material would perform to its potential at all angles.

[KelvinS1965]

I just went back over my readings for my recent calibration on my AE3000 and Beamax screen. I use minimum zoom for 16:9 viewing on my 2.35:1 screen (ie the dimmest, but highest contrast). With 100 IRE full field test pattern I measured 5.1fL off the screen using my eye-one LT probe. This seems low even given the size of my screen and that Cinema 1 is known as being a 'dim' mode, though more accurate than 'Normal' or 'Dynamic'.

I compared this to Cine4home's review that gave 300 lumens for minimum zoomin Cinema 1 mode and eco lamp setting. Using some calculations provided IIRC by Gary Lightfoot I created a spreadsheet that works out fL and it gave me 15.8fL assuming the screen really is 1.5 gain.

My PJ has 130 hours on it, but even assuming a 20% drop in brightness that would still equal 240 lumens which gives 12.6fL, still a long way from my measured 5.1fL. I realise that an eye-one LT isn't the most accurate device, but I would have though it wasn't under reading by 50% or more, so it makes me think that my 1.5 gain screen is no more than 1.0 and the rest of the difference could be down to tolerances between my AE3000 and the tested example, plus errors in the eye-one. Kind of disapointing though and to back it up I feel the image isn't bright enough, which strangely effects the dark scenes. I suppose I could have been wrongly supplied with the 1.2 gain version; I'd have no way of checking this though apart from being told that the 1.5 gain has a black backing (mine has).

[warbie]

It sounds like you have the 1.5 gain material, Kelvin. The sample I have has a black back too.

Cheers for the info. btw Custard. You're probably right about the material, although it never gets near to the brightness of the primer regardless of where you look at it from.

[markswift2003]

Originally Posted by KelvinS1965

I just went back over my readings for my recent calibration on my AE3000 and Beamax screen. I use minimum zoom for 16:9 viewing on my 2.35:1 screen (ie the dimmest, but highest contrast). With 100 IRE full field test pattern I measured 5.1fL off the screen using my eye-one LT probe. This seems low even given the size of my screen and that Cinema 1 is known as being a 'dim' mode, though more accurate than 'Normal' or 'Dynamic'.

I compared this to Cine4home's review that gave 300 lumens for minimum zoomin Cinema 1 mode and eco lamp setting. Using some calculations provided IIRC by Gary Lightfoot I created a spreadsheet that works out fL and it gave me 15.8fL assuming the screen really is 1.5 gain.

My PJ has 130 hours on it, but even assuming a 20% drop in brightness that would still equal 240 lumens which gives 12.6fL, still a long way from my measured 5.1fL. I realise that an eye-one LT isn't the most accurate device, but I would have though it wasn't under reading by 50% or more, so it makes me think that my 1.5 gain screen is no more than 1.0 and the rest of the difference could be down to tolerances between my AE3000 and the tested example, plus errors in the eye-one. Kind of disapointing though and to back it up I feel the image isn't bright enough, which strangely effects the dark scenes. I suppose I could have been wrongly supplied with the 1.2 gain version; I'd have no way of checking this though apart from being told that the 1.5 gain has a black backing (mine has).

To give you some comparison, My screen is a Screenline Copernico (variable aspect, constant image width). This uses a material called DLP2006 which has a gain of 1.0.

The PJ is at 4.5M from the screen which is 2.9M wide. 100Hrs on the bulb, eco setting.

I get the following readings on full field at 100IRE using a Spyder3


Normal:

UnCal: 12ftL
Cal: 10.5ftL

Colour1:

Uncal: 4.6ftL
Cal: 6.4ftL

Cinema1

Uncal: 5.9ftL
Cal: 6.5ftL


Subjectively, Both Cinema1 & Colour1 are plenty bright enough.

Mark